T  H 


73* 


IRLF 


SB    Eb    022 


!!!!! 


REESE  LIBRARY 

OF  THK 

UNIVERSITY  OF  CALIFORNIA. 

Deceived  ,  igo     . 

^Accession  No.      '20J6      .   Class  No. 


MILL  BUILDING   • 

CONSTRUCTION 


BY 


H.    G     TYRRELL,    C.  E 

Bridge  and  Structural  Engineer 


UNIVERSITY 


NEW  YORK 

THE  ENGINEERING  NEWS  PUBLISHING  CO. 

1901 


Copyright,  1901.  by 
THE  ENGINEERING  NEWS  PUBLISHING  COMPANY 


TABLE  OF  CONTENTS. 


CHAPTER  I. 

Loads  :  Roof  Loads — Floor  Loads — Crane  Loads — Snow  and 
Wind  Loads — Miscellaneous  Loads — Summary  of  Loads — Meth- 
ods of  Calculation. 

CHAPTER  II. 

General  Design :  General  Considerations — Walls — Roof  Trusses 
— Spacing  of  Trusses — Jack  Rafters — Roof  Coverings — Truss 
Connections — Rafters — Bottom  Chords — Purlins — Unit  Stresses — 
Lighting  and  Ventilation — Estimating  the  Cost. 

CHAPTER  III. 

Design  of  Structural  Details:  Foundations  and  Anchorages. 
Ground  Floor  Construction :  Concrete  Floors — Asphalt  Floors — 
Wood  Floors — Floors  for  Car  Sheds.  Upper  Floor  Construc- 
tion: Steel  Trough  Floors — Corrugated  Iron  and  Brick  Arch 
Floors — Steel  Girder  and  Timber  Floors — Slow  Burning  Wood 
Floors.  Roof  Coverings:  General  Considerations — Slate  Roofing 
— Asphalt  Roofing — Slag  and  Gravel  Roofing — Corrugated  Iron 
Roofing — Sheet  Steel  Roofing — Crimped  Roofing — Steel  Roll 
Roofing — Tin  and  Terne  Plate  Roofing — Metal  Shingle  Roofing — 
Rubber  Roofing — Asbestos  Roofing — Wood  Shingle  Roofing — 
Comparative  Costs  of  Roofing.  Miscellaneous  Structural  Details : 
Wall  Anchorages  of  Roof  Trusses — Doors  and  Windows — Ventila- 
tion— Gutters  and  Down  Spouts. 

92016 


CHAPTER  I. 
LOADS. 

Mill  buildings  differ  so  greatly  in  character  and  purpose  that  it 
is  impossible  to  formulate  tables  of  dead  weights  which  will  suit  all 
cases.  The  use  to  which  the  building  is  to  be  put,  its  location,  the 
character  of  the  roof  covering,  the  presence  or  absence  of  cranes, 
etc.,  all  affect  the  dead  weight,  and  generally  each  case  must  be  con- 
sidered individually.  For  most  purposes  of  design  the  loads  may 
be  divided  into  :  (i)  roof  loads ;  (2)  floor  loads ;  (3)  crane  loads ; 
(4)  snow  and  wind  loads,  and  (5)  miscellaneous  loads. 

ROOF  LOADS. — For  making  rough  estimates  the  diagram  of 
weights  of  roof  trusses  given  in  Fig.  I  will  prove  useful.  These 
weights  have  been  figured  separately  and  do  not  quite  agree  with 
any  of  the  published  formulas.  From  this  diagram,  the  table  (Table 
I.)  giving  the  weights  of  roof  coverings  and  the  table  (Table  III.) 
of  wind  and  snow  loads,  the  total  weight  to  be  carried  is  found. 
Were  it  possible  to  realize  in  actual  practice  the  small  sections  re- 
quired, the  weight  of  trusses  would  be  directly  proportional  to  the 
load  carried.  Iron  purlins  weigh  from  2  Ibs.  to  4  Ibs.  per  square 
foot  of  ground  covered,  according  to  the  spacing  of  the  trusses. 
Good  practice  in  the  United  States  requires  that  roofs  in  northern 
latitudes  shall  be  figured  for  at  least  40  Ibs.  per  square  foot  of  roof 
surface. 

FLOOR  LOADS.— The  Building  Law  of  New  York  City  re- 
quires that  floors  shall  be  proportioned  to  carry  the  following  min- 
imum loads  per  square  foot:  Office  buildings,  100  Ibs.;  public 
halls,  120  Ibs.;  stores,  factories,  warehouses,  etc.,  150  Ibs.;  floors 
carrying  heavy  machinery,  250  Ibs.  to  400  Ibs.  In  every  case  the 
floor  must  be  strong  enough  to  carry  its  maximum  load.  Mr.  C. 
J.  H.  Woodbury,  in  his  book  on  "The  Fire  Protection  of  Mills/' 
gives  a  table  of  weights  per  square  foot  of  floor  of  various  kinds 
of  merchandise,  which  is  reprinted  herewith  (Table  I.)  and  which 
will  be  found  valuable  in  determining  loads  on  floors. 

CRANE  LOADS. — For  small  traveling  cranes  of  one  or  two 
tons  capacity  it  is  safe  to  consider  the  total  weight  of  one  end  of  the 
crane  and  its  load  as  twice  the  capacity  of  the  crane.  For  cranes 


MILL     BUILDING     CONSTRUCTION. 


w*  = 


WKpersq.-fk  of  Ana 


MINIMI 


of  larger  capacities  Table  II.  gives  the  maximum  weight  which  will 
come  on  two  carrying  wheels  at  one  end  of  the  crane  when  the 
fully  loaded  trolley  is  at  that  end.  The  corresponding  figures  for 
the  other  end  would  be  somewhat  smaller,  but  not  enough  so  to 
affect  materially 
the  construction 
of  the  building. 
From  the  fig- 
ures in  Table  II. 
the  strength  of 
traveling  crane 
runway  girders 
and  c  olu  m  n  s 
may  be  calcu- 
lated. 

The  strains 
due  to  the  pres- 
e  n  c  e  of  jib 
cranes  vary  so 
greatly  in  num- 
b  e  r,  character 
and  intensity  in 
different  cases, 
that  they  do  not 
admit  of  a  n  y 
general  tabular 
statement.  They 
must,  however, 
be  carefully  fig- 


Weight of  Roof  Trusses   per  sq.  -ft   of  Area   Covered. 


7000 


6000 


•  4000 


3000 


8000 


1000 


Z'-V. 


30 


80 


90 


ured    in    each 

case    and    fully 

provided  for  in 

the  design.  The 

principal  strains 

produced  will  be 

in    the    lower 

chord  bracing  of 

the    roof   trusses,    and    the    bending    strains    in    the    supporting 

columns. 

SNOW  AND  WIND  LOADS.— The  pressure  exerted  by  wind 
on  roofs  is  in  every  case  normal  to  the  plane  of  the  roof  surface. 


40  50          60 

Total   Weight  of  Roof 
Capacity  40  fee.  per  sq,  -fr.    Units  C/JOO,  15,000.  PHch  6"  per  ft 

Fig.  1.     Diagrams  Showing  Weights  of  Roof  Trusses. 


LOADS.  5 

The  amount  of  wind  pressure  usually  assumed  in  proportioning 
framed  structures  is  30  Ibs.  per  square  foot  on  a  Vertical  surface, 
which  corresponds  to  a  velocity  of  from  70  to  80  miles  per  hour. 
This  velocity  includes  all  storms  except  tornadoes,  which  cannot  be 
provided  for.  Table  III.  gives  the  normal  pressures  on  roof  sur- 
faces of  different  slopes  for  a  pressure  of  30  Ibs.  per  square  foot 
on  a  vertical  surface. 

Snow  loads  of  from  10  Ibs.  to  20  Ibs.  per  square  foot  of  horizontal 
projection  of  the  roof  should  be  provided  for.  There  are  records 
of  snow  and  ice  deposits  weighing  40  Ibs.  per  square  foot  having 
formed  on  roofs  in  northern  latitudes,  but  this  is  a  very  exceptional 
occurrence.  When  the  roof  has  a  pitch  of  45°  or  more,  snow  load 
need  not  be  considered.  In  New  England  latitudes,  for  roofs  of 
ordinary  pitch,  it  will  be  sufficient  to  assume  30  Ibs.  per  square  foot 
of  roof  surface  for  snow  and  wind  loads  combined.  The  maximum 
strains  from  wind  and  jib  crane  loads  will  so  seldom  occur  together 
in  the  horizontal  bracing  that  a  combination  need  not  be  provided 
for.  If  they  should  occur  at  the  same  time,  once  in  a  year  or  so, 
the  factor  of  safety  will  enable  the  metal  to  withstand  the  strain 
without  injury. 

The  overturning  effect  of  wind  acting  on  the  building  as  a  whole 
and  tending  to  revolve  it  about  the  bases  of  the  leeward  columns 
need  be  considered  only  in  the  case  of  tall  narrow  buildings.  Wind 
acting  on  the  sides  of  a  building  will  necessitate  the  use  of  knee 
braces  running  from  the  columns  to  the  bottom  chords  of  the  roof 
trusses,  and  the  strains  in  these  braces  will  be  considerable.  These 
strains  will  produce  bending  strains  in  the  columns  which  must  be 
provided  for. 

MISCELLANEOUS  LOADS.— In  special  cases  'there  will  be 
other  loads  to  provide  for  besides  the  more  common  roof,  floor, 
crane,  snow  and  wind  loads  just  considered.  The  bottom 
chords  of  roof  trusses  are  frequently  employed  to  carry  shafting, 
steam  pipes,  trolleys,  etc.  It  is  sometimes  convenient  also  to  have 
the  roof  trusses  sufficiently  strong  to  permit  of  a  block  and  tackle 
being  attached  at  any  point  to  handle  goods.  The  roof  may  re- 
quire a  ventilator  and  when  it  does  this  extra  weight  must  be  added 
to  the  roof  loads.  Columns  in  exposed  places  where  they  are  liable 
to  shocks  from  vehicles  or  merchandise  should  be  made  stronger 
than  those  built  into  brick  walls. 

SUMMARY  OF  LOADS.— The  total  roof  loads  per  square 

TuBS 

OF  THE 

UNIVERSITY 


6  'MILL     BUILDING     CONSTRUCTION. 

foot  of  roof,  including  weights  of  trusses  for  spans  under  75  ft.,  is 
about  as  follows  for  different  constructions  of  roofing: 

Style  of  Construction.  Lbs.  per  sq.  ft. 

Corrugated  iron,  unbearded 8 

"  "      on  boards 11 

Slate  on  laths 13 

"       "    r»4-in.    boards 16 

Tar  and  gravel 12 

Shingles  on  laths , 10 

Tile 20-30 

When  any  of  these  roofs  are  plastered  below  the  rafters  10  Ibs. 
per  square  foot  should  be  added  to  the  loads  given.  For  spans 
greater  than  75  ft.  a  weight  of  4  Ibs.  per  square  foot  should  be 
added  to  the  weights  given.  For  snow  and  wind  loads  combined 
add  for  northern  latitudes  30  Ibs.  per  square  foot  to  the  loads  given. 

The  weight  of  steel  in  the  sides  and  roofs  of  mill  buildings,  with- 
out cranes,  is  from  4  Ibs.  to  6  Ibs.  per  square  foot  of  exposed  sur- 
face for  the  frame  only.  Corrugated  iron  sheathing  weighs  from 
i  Ib.  to  2,  Ibs.  per  square  foot.  These  weights,  with  steel  at  5  cts. 
per  Ib.,  make  the  cost  of  steel  buildings  from  25  cts.  to  40  cts.  per 
square  foot  of  exposed  surface.  A  rough  approximate  rule  for 
calculating  the  extra  weight  of  steel  required  in  columns  and  girders 
when  traveling  cranes  are  used  is  as  follows :  Add  100  Ibs.  of  steel 
per  lineal  foot  of  building  for  every  five  tons  of  crane  capacity. 
This  would  give  for  a  5-ton  crane  an  addition  of  100  Ibs.  per  lineal 
foot  and  for  a  2O-ton  crane  an  addition  of  400  Ibs.  per  lineal  foot. 

METHODS  OF  CALCULATION.— Methods  of  calculation 
will  not  be  touched  upon  in  this  book,  since  they  may  be  found  in 
any  text-book  upon  the  subject.  Briefly  enumerated,  the  cases  to  be 
considered  in  determining  strains  are  the  following: 

(1)  Strains  in  roof  trusses  and  columns  from  permanent  dead 
loads. 

(2)  Roof  trusses  on  walls,  strains  from  wind  normal  to  the  sur- 
face. 

(3)  Wind  on  side  of  building  and  roof,  strains  in  trusses,  columns 
and  knee  braces ;  (a)  columns  hinged  at  the  base ;  (b)  columns  fixed 
at  the  base. 

Partial  loading  can  never  cause  maximum  srains  in  the  parts  of 
a  Fink  truss  as  they  may  in  other  forms  of  roof  trusses. 


LOADS. 


TABLE    I.— Showing  Weights   of  Merchandise  as  Given  by  C.  J.  H.  Woodbury  in 
his  Book  on  "Fire  Protection  of  Mills." 

Wool  in  bales 17  to  2&  Ibs.  per  cu.  ft. 

Woolen  goods 16  to  22 

Baled  cotton 20  to  40 

Cotton  goods 16  to  40 

Rags  in  bales 15  to  36 

Strawboard,  newspaper  and  manilla 33  to  44 

Calendered  and  super-calendered  book 50  to  70 

Writing  and  wrapping  paper 70  to  90 

Wheat 39  to  44 

Flour 40 

Corn 31 

Corn  meal 37 

Oats 27 

Baled   hay 57 

Compressed  hay  and  straw 19  to  30 

Bleaching  powder 31 

Soda   ash 62 

Indigo 43 

Cutch 45 

Sumac 39 

Caustic  soda 88 

Starch 23 

Alum 33 

Extract  logwood 70 

Lime 50 

Cement,   American 59 

Cement,  English 73 

Plaster 53 

Rosin 48 

Lard  oil 34 

Rope 42 

Tin 278 

Glass 60 

Crockery 40 

Leather  in  bales 16  to  23 

Sugar 42 

Cheese.  .  30 


TABLE  II.— Showing  Maximum  Weight    in    Pounds    Which    Will    Come    on    End 
Wheels  of  Traveling  Crane  When  the  Fully-Loaded  Trolley  is  at  the  Same 
End. 

Capacity,     i —Span  of  crane  in  feet. 1 

in  tons.        25  30  35  40  45  50  55  60 

5 31,700      32,870      33,800       34,900     35,900     37,200     38,600     40,300 

10 45,100      46,000      47,400       48,900     50,200     51,600     53.200     55,700 

20 72,100      74,100      75,800       77,600      79,400     82,000     83,900     86,100 

30 103,800    108,200    110,000     112,600    115,200   117,700   120,400    122,800 

50 152,300    158,100    162,200     167,500    171,600   175,600    178,600    182,400 


TABLE  III. — Giving  the  Normal   Pressures    from    Wind    on  Roofs    of    Different 

Slopes  for  a  Wind  Pressure  of  30  Ibs.    per    Square  Foot  Against    a    Vertical 
Plane. 

Angle.          Pressure.        Angle.          Pressure.  Angle.         Pressure. 

5                 3.9               25               16.9  45  27.1 

10                  7.2                30                19.9                50  28.6 

15               10.5               35               22.6               55  29.7 

20                13.7                40                25.1                60  30.0 


CHAPTER  II. 
GENERAL  DESIGN. 

In  every  case  the  use  to  which  a  building  is  to  be  put  will  in  a 
great  measure  determine  the  character  of  its  general  structural  feat- 
ures. A  building  may  or  may  not  require  to  be  heated  in  winter ; 
it  may  or  may  not  need  to  be  well  lighted,  and  it  may  require  a 
heavy  or  a  light  construction.  With  these  general  facts  in  mind 
we  are  in  position  to  consider  the  questions  of  general  design. 

GENERAL  CONSIDERATIONS.— In  determining  the  size  of 
an  iron  building,  in  case  the  ground  room  is  unlimited,  it  is  well 
to  locate  first  the  machinery  to  the  best  advantage  to  turn  out 
products  at  the  minimum  cost,  and  afterwards  to  decide  on  the 
size  and  shape  of  the  building  to  suit  the  machinery.  If,  however, 
the  amount  of  ground  is  limited,  this  cannot  be  done,  as  the  build- 
ing will  cover  only  the  limits  of  the  lot.  It  is  well  also  to  consider 
whether  or  not  the  proposed  building  is  to  be  a  permanent  one. 
If  for  temporary  purpose,  unit  strains  may  be  taken  high  and  the 
first  cost  of  construction  cut  down  to  the  very  lowest  limit.  If, 
however,  the  building  is  to  be  permanent,  this  is  not  desirable,  as  it 
is  frequently  found  that  heavier  loads  and  greater  strength  is  re- 
quired than  at  first  anticipated.  It  is  the  practice  of  the  writer,  after 
making  his  original  design,  to  go  over  the  plans  a  second  time  and 
rearrange  and  omit  all  unnecessary  pieces,  at  the  same  time  add- 
ing bracing  where  it  may  be  found  necessary.  Stiffness  in  the 
whole  construction  should  be  one  of  the  principal  ends.  There  are 
more  steel  buildings  throughout  the  country  going  to  ruin  on  acj 
count  of  insufficient  bracing  than  perhaps  from  any  other  cause. 
Steel  will  easily  stand  being  strained  nearly  up  to  the  elastic  limit 
without  serious  injury,  but  lack  of  stiffness  is  liable,  not  only  to  de- 
stroy the  frame  itself,  but  the  covering  and  glass,  at  the  same  time 
cause  shafting  to  get  out  of  line,  and  traveling  cranes  to  bind  and 
run  untrue.  It  is  frequently  the  intention  in  constructing  a  building 
to  plan  for  future  extension  at  one  or  both  ends.  Provision  can 
well  be  made  for  this  by  placing  regular  trusses  at  the  ends  and  put- 
ting in  temporary  posts  up  to  the  height  of  the  bottom  chord  to 
support  the  end  purlins.  Then  when  extension  is  desired  the  end 
covering  can  be  removed  and  these  posts  taken  out  to  be  used  again 
in  the  new  end. 


GENERAL  DESIGN.  g 

WALLS. — The  wall  construction  most  commonly  employed  in 
mill  buildings  is :  Solid  brick  walls ;  iron  columns  with  brick  cur- 
tain walls,  or  iron  columns  and  purlins  covered  with  corrugated 
iron.  Concrete  filling  between  steel  columns  has  occasionally  been 
employed  for  side  walls,  but  it  is  somewhat  more  expensive  than 
brick  filling  on  account  of  the  temporary  timber-work  required  to 
keep  it  in  place  while  hardening  and  also  because  a  light  permanent 
iron  frame  is  necessary  to  hold  the  windows  in  position.  Of  the 
forms  of  construction  named,  corrugated  iron  is  the  cheapest  and 
most  easily  renewed,  but  it  cannot  be  used  for  buildings  which  are 
to  be  heated.  Machine  shops,  electric  light  stations,  and  similar 
buildings  must  have  solid  walls,  and  if  the  height  is  not  great  or 
if  the  loads  are  not  excessive,  brick  walls  will  be  the  cheapest  con- 
struction. Brick  walls  make  a  rigid  construction  suited  to  with- 
stand the  action  of  cranes  and  heavy  machinery.  In  case  the  walls 
are  required  to  be  very  thick  under  trusses,  the  most  economical 
construction  will  be  iron  columns  with  curtain  walls.  This  con- 
struction is  usually  less  rigid  than  solid  brick  walls,  and  it  is  con- 
sequently not  so  serviceable  for  buildings  having  heavy  traveling 
cranes.  In  special  cases,  where  sand  and  gravel  are  plentiful,  and 
where  bricks  are  expensive,  a  concrete  filling  between  the  wall  col- 
umns is  less  expensive  than  brick,  and  is  in  every  way  just 
as  serviceable.  Where  columns  with  curtain  walls  are  em- 
ployed, the  tops  of  the  columns  should  be  connected  by 
steel  struts  to  keep  them  in  position.  Columns  with  brac- 
ing between  them  in  a  vertical  plane  make  as  stiff  a  con-  Fig  2 
struction  as  can  be  secured,  and  consequently  are  well 
suited  for  heavy  cranes  and  machinery. 

The  form  and  section  of  column  employed  varies  greatly.  For 
light  loads  four  angles  latticed  together,  as  shown  by  Fig.  2,  is 
•a  construction  frequently  used,  and  the  column  must  be  given  suffi- 
cient width  to  take  the  bending  strains  from  the  knee  braces.  If 
brick-work  is  to  be  built  into  the  columns,  their  width  must  be 
made  to  suit  the  size  of  the  brick.  It  may  sometimes  be  desirable 
to  have  one  or  more  large  bays  or  wide  panels  in  the  walls,  in  which 
case  the  ends  of  the  roof  trusses  coming  over  these  bays  must  be 
supported  on  side  or  wall  girders  attached  to  the  columns  on  each 
side  of  the  bay. 

ROOF  TRUSSES. — The  Fink  truss  is  the  type  most  commonly 
used  in  the  United  States  for  the  roofs  of  small  buildings.  It  is 
economical  because  most  of  its  members  are  in  tension  and  the 


i 


10 


MILL     BUILDING     CONSTRUCTION. 


Fig.  5. 


Fig.8. 

Figs.    3    to    8.     Diagrams    of    Common 
Forms  of  Roof  Trusses. 


struts  are  short.  Fig.  3  is  the  form  of  Fink  truss  commonly  used 
for  spans  of  from  30  ft.  to  40  ft. ;  Fig.  4,  the  form  used  for  spans  of 
from  40  ft.  to  55  ft.;  Fig.  5,  the  form  used  for  spans  of  from  55  ft. 
to  85  ft. ;  and  Fig.  6,  the  forms  used  for  spans  of 
from  85  &•  to  100  ft.  If  the  slope  of  the  roof  is 
small,  some  form  of  English  truss  will  be  prefer- 

to  tne  Fink  truss,  because 
ives  ketter  intersection 
angles-  If  the  roof  is  hipped  it 
*s  necessar7  to  have  vertical 
members  to  which  to  fasten 
the  hip  rafters.  Figs.  7  and  8, 
respectively,  show  a  Queen 
truss  and  a  Fink  truss  of  the 
same  span  and  pitch,  and  both 
with  vertical  posts.  It  will  be 
observed  that  the  longest  ver- 
tical strut  in  the  Queen  truss  is  avoided  in  the  Fink  truss. 

For  small  spans  up  to  say  30  ft.,  sheets  of  corrugated  iron  may 
be  curved  and  provided  with  a  single  tie-rod  across  the  bottom  to 
form  an  arched  roof.  This  construction  can  often  be  used  to  ad- 
vantage for  ventilator  roofs. 

The  allowable  slope  or  pitch  of  roofs  depends  upon  the  kind  of 
covering  or  roofing  employed.  The  allowable  slopes  for  some  of 
the  more  common  roof  coverings  are  shown  in  Table  IV.  It  is 
more  economical  to  employ  horizontal  bottom  chords  for  roof 
trusses,  or  at  least  to  keep  the  cumber  dowrn  to  an  inch  or  two, 
since  it  avoids  any  bending  of  the  bottom  chord  laterals.  A  truss 
whose  bottom  chord  has  a  rise  of  two  or  three  feet,  however,  pre- 
sents a  better  appearance.  The  neutral  axes  of  all  chord  members 
should  intersect  in  a  common  point  at  each  intersection.  Flat  iron 
should  not  be  used  in  roof  trusses,  except  for  connection  plates,  as 
it  lacks  the  necessary  stiffness.  Steel  is  a  superior  material  to  tim- 
ber for  roof  trusses,  because  it  is  lighter,  stronger  and  more  dur- 
able. 

SPACING  OF  TRUSSES.— For  the  least  weight  of  purlins  the 
distance  between  supports  must  be  a  minimum,  and  since  the 
weight  of  trusses  is  directly  proportioned  to  the  load  upon  them, 
the  least  total  weight  of  trusses  and  purlins  will  be  when  the  trusses 
are  placed  close  together.  This  reasoning  assumes  that  it  is  possible 
to  realize  practically  the  small  sections  required  for  the  truss  mem- 


GENERAL  DESIGN.  H 

bers,  which  it  is  plainly  impossible  to  do.  Experience  shows  that 
the  most  economical  distance  between  centers  of  trusses  for  small 
spans  up  to  say  50  ft.,  is  from  10  ft.  to  16  ft.;  for  spans  exceeding 
50  ft.  it  should  be  from  one-fourth  to  one-eighth  of  the  span,  de- 
pending upon  the  nature  of  the  roof  covering  and  purlins. 

For  plank  laid  directly  on  rafters  spacing  should  not  exceed  8  ft. 
for  2-in.  plank  and  10  ft.  for  3~in.  plank. 

JACK  RAFTERS. — Jack  rafters  need  not  ordinarily  be  used  in 
mill  buildings.  When,  however,  the  distance  between  trusses  ex- 
ceeds 20  ft.,  it  will  be  more  economical  of  material  to  run  a  few 
heavy  purlins  from  truss  to  truss  to  carry  one  or  more  jack  rafters 
which  in  turn  support  the  small  purlins  upon  which  the  roof  cov- 
ering rests.  This  construction  was  used  in  most  of  the  buildings 
for  the  Columbian  Exposition  at  Chicago  and  in  many  of  the  roofs 
for  large  train  sheds  which  have  recently  been  constructed. 

ROOF  COVERINGS.— A  great  variety  of  roof  coverings  are 
available  to  the  engineer.  In  selecting  a  roof  covering  the  princi- 
pal things  to  be  considered  are  the  cost  and  the  necessity  or  not  of 
having  it  fire-proof  Figures  of  slopes  required  for  various  ordi- 
nary kinds  of  roof  coverings  are  given  in  Table  IV.  It  should  be 
remembered  that  the  material  requiring  the  greatest  slope  will  re- 
quire the  largest  amount  of  covering. 

TABLE  IV. — Showing  Least  Pitch  of  Roof  Required  for  Various  Kinds    of  Roof 

Coverings. 

Wood   shingles  on  plank least  pitch  =    Vt  span. 

Slate,    large =    Vs 

"        ordinary =    V* 

"        in  cement =    Ve 

Steel    roll    roofing =  Vis 

Rubber =  Via 

Asbestos =  Via 

Asphalt =  Via 

Corrugated  iron  laid  in  cement —    Vs 

"    not  laid  in  cement =    Vi 

Tar  and  gravel flat 

Tin  or  terne  plates " 

The  building  laws  of  the  principal  cities  specify  the  conditions 
tinder  which  fire-proof  roof  coverings  shall  be  used  and  also  state 
what  coverings  are  to  be  classed  as  fire-proof.  Where  this  matter 
is  not  specified,  the  engineer  must  decide  whether  or  not  the  risk 
warrants  the  use  of  fire-proof  roofing,  keeping  in  mind  always  that 
the  cost  of  insurance  on  fire-proof  buildings  is  less  than  for  build- 
ings which  do  not  come  within  this  classification.  When  the  risk 
is  inconsiderable  a  covering  of  some  of  the  best  brands  of  roofing 
paper  makes  in  every  respect  a  first-class  roof,  since  this  material 


12  MILL     BUILDING     CONSTRUCTION. 

is  cheap,  is  easily  applied,  will  last  for  years,  and  does  not  transmit 
cold  as  do  metal  or  slate.  Metal  roofing  is  soon  destroyed  in  build- 
ings where  corrosive  gases  accumulate.  If  warm  air  comes  in  con- 
tact with  the  underside  of  the  roof  the  covering  should  be  laid  on 
boards  or  have  some  kind  of  anti-condensation  lining.  Figures 
showing  the  comparative  costs  of  different  kinds  of  roof  coverings 
are  given  in  Table  IX. 

TRUSS  CONNECTIONS.— The  choice  between  the  use  of  bolts 
or  of  pins  for  truss  connections  is  determined  in  each  case  by  the 
relative  cost  of  manufacture  and  erection.  Generally  for  small 
trusses  bolted  connections  are  very  much  the  cheaper,  but  for 
trusses  of  long  span,  where  erection  may  be  difficult  or  expen- 
sive, pin  connections  can  be  employed  to  greater  advantage. 

RAFTERS. — The  most  common  form  of  rafter  is  one     "~jj| 
made  up  of  two  angles  arranged  as  shown  by  Fig.  9,  and 
having  gusset  plates  between  the  adjacent  flanges  at  the 
panel  point  connections.     If  the  load  is  uniformly  distrib-     Fig.  9. 
uted,  this  form  of  rafter  should  have  a  continuous  web  riv- 
eted between  the  angles  to  resist  the  bending  strain,  instead  of  the 
separate  gusset  plates  at  connections  only.     When  the  loads  are 
concentrated  at  the  panel  points  they  should  be  located  as  nearly  as 
possible  directly  over  the  sub-struts. 

BOTTOM  CHORDS.— For  all  ordinary  cases  the  bottom 
chords  of  roof  trusses  may  be  made  of  two  angles  placed  back  to 
back.  If,  however,  it  is  desired  to  have  stiff  chords  to  which 
weights  can  be  safely  attached  at  any  point,  two  channels  riveted 
back  to  back  should  be  used.  When  jib  cranes  are  used  there 
should  be  a  horizontal  bracing  between  the  roof  trusses  in  the  plane 
of  the  bottom  chords. 

PURLINS. — Angles,  channels,  Z-bars  and  I-beams  are  all  used 

for  purlins.  Angles,  channels  and  Z- 
bars  are  fastened  to  the  rafters  by  an- 
gle clips,  Fig.  10,  but  I-beams  are 
usually  bolted  directly  to  the  rafter. 

An  angfle  trussed  with  a  tension  rod 
Fig.  10.    Clip  Connection  Between  . 

Purlin  and  Rafter.  and  center  strut  is  a  form  of  purlin 

sometimes  employed,   but   ordinarily 

simple  shapes  without  trussing  are  preferable,  since  too  much  truss- 
ing and  bracing  injures  the  appearance  of  the  roof  and  adds  to  the 


GENERAL  DESIGN.  13 

cost  of  manufacture.  It  is  more  economical  to  use  simple  shapes 
even  at  the  expense  of  increasing  the  weights  slightly  than  it  is  to  in- 
troduce trussing.  When  the  distance  between  rafters  is  more  than 
about  15  ft.  a  line  of  f-in.  rods  should  be  run  from  the  ridge  through 
the  purlins  to  prevent  them  from  sagging  in  the  plane  of  the  rafters. 
At  the  gable  walls  a  single  angle  may  be  built  into  the  masonry  and 
the  purlins  attached  to  it  by  clips  as  they  would  be  attached  to  a 
rafter. 

The  best  way  of  placing  angle  purlins  on  a  sloping  roof  is  as 
shown  in  the  sketch,  Fig.  loa.  In  this  position  it  has  a  greater  ver- 
tical moment  of  resistance  than  if  the 
roof  leg  were  placed  in  a  reverse  posi- 
tion, as  in  Fig  lob.  To  rivet  the  over- 
lapping ends  of  the  corrugated  iron  on 
both  sides  of  the  angle  purlin,  as  shown 

in  the  sketch,  Fig.  IDC,  and  securing  S^  ^  fig.  10  c. 
the  covering  to  the  angle  by  means 
of  a  bent  iron,  passing  around  the  purlin,  makes  altogether  a  very 
much  tighter  piece  of  work  than  for  a  single  clinch  nail  to  be  driven 
through  the  sheathing  and  bent  around  one  leg  of  the  purlin.  In 
order  to  protect  the  overhanging  corrugated  iron  at  the  eave  from 
being  battered  and  getting  out  of  shape  it  is  desirable  to  extend  the 
upper  chord  angles  of  the  trusses  out  far  enough  to  receive  an  out- 
.side  purlin  placed  as  nearly  as  possible  at  the  edge  of  the  sheath- 
ing. This  overhang  need  not  be  greater  than  12  or  15  ins.,  and 
if  a  slightly  better  appearance  is  desired  a  molded  sheet  metal  cor- 
nice may  be  used. 

UNIT  STRESSES. — For  dead  and  for  live  load  stresses  a  factor 
•of  safety  of  four  is  sufficient.  For  greater  combinations  such  as 
dead,  live,  wind  and  crane  loads  combined,  a  factor  of  safety  of 
three  should  be  used.  The  temporary  buildings  for  the  Columbian 
Exposition  at  Chicago  were  proportioned  for  unit  tensile  strains 
of  from  20,000  Ibs.  to  25,000  Ibs.  per  square  inch  of  section. 

LIGHTING  AND  VENTILATION.— A  very  efficient  method 
of  lighting  mill  buildings  is  to  make  the  entire  upper  halves  of  the 
side  walls  of  windows  with  the  sash  bolted  to  the  framing.  In 
buildings  which  do  not  require  heating  in  cold  weather,  such  as 
forge  shops  and  boiler  houses,  the  lower  halves  of  the  side  walls 
may  be  made  of  wood  panels  which  can  be  easily  removed  to  allow 
,a  free  circulation  of  air  and  to  give  clear  space  for  the  handling  of 


14  MILL     BUILDING     CONSTRUCTION. 

material.  Windows  in  the  sides  of  monitor  roofs  admit  light  to  the 
upper  part  of  the  building  only ;  they  throw  very  little  light  to  the 
floor.  Translucent  wire  cloth  may  be  used  for  skylights,  but  it 
collects  dust  and  smoke  and  becomes  soft  in  warm  weather.  In 
cases  where  the  movement  of  heavy  cranes  and  the  jar  of  steam 
hammers  and  running  machinery  cause  sufficient  vibration  to  break 
glass  skylights,  the  translucent  wire  cloth  may  be  used  to  advan- 
tage, but  it  must  be  frequently  cleaned.  Continuous  monitor  roofs 
with  open  sides  are  usually  sufficient  to  ensure  ventilation.  In 
forge  shops  or  other  buildings  where  there  is  considerable  gas  and 
smoke  the  monitor  roof  may  be  rendered  much  more  efficient  as  a 
ventilator  by  placing  a  line  of  shutters  about  2  ft.  high  in  the  side 
walls  at  their  bottoms.  When  these  shutters  are  opened  an  up- 
ward draft  is  secured  through  them  and  the  open  sides  of  the  mon- 
itor roof. 

A  good  common  rule  for  the  amount  of  windows  required  in  the 
side  of  a  building  is  to  make  the  window  area  one-fifth  of  the  walls, 
or  say  one-tenth  of  the  total  floor  area.  In  place  of  removable 
wooden  panels  for  the  sides,  corrugated  iron  doors  may  sometimes 
be  used  to  advantage.  These  are  built  to  fill  the  whole  panel  and 
are  counter  weighted.  They  can  be  easily  opened,  but  on  account 
of  the  counter  weights  and  rigging  for  hanging  them,  the  cost  is 
considerably  more  than  that  of  wooden  panels.  If  sash  is  used  in 
the  side  monitor  for  the  purpose  of  securing  light,  then  this  mon- 
itor should  be  wide,  say  one-fourth  the  whole  width  of  the  building, 
in  order  to  allow  light  to  reach  the  floor.  This  arrangement  of 
wide  monitor,  however,  does  not  secure  so  good  ventilation.  The 
upper  part  of  the  roof  holds  a  considerable  amount  of  dead  air. 
To  overcome  this  a  second  smaller  monitor  may  be  placed  along 
the  ridge  with  louvres  or  shutters  on  the  sides.  This  arrangement 
will  secure  both  a  light  interior  and  good  ventilation. 

ESTIMATING  THE  COST.— It  has  already  been  stated  that 
the  weight  of  steel  frames  for  mills  and  similar  buildings  is  from 
4  Ibs.  to  6  Ibs.  per  sq.  ft.  of  exposed  wall  and  roof  surface;  also 
that  provision  for  traveling  crane  adds  a  weight  of  about  100  Ibs. 
per  lin.  ft.  of  building  for  every  five  tons  capacity  of  crane.  Other 
material,  such  as  brick  wall,  roofing,  doors,  windows  and  floors,  is 
very  easily  figured  out  in  square  feet.  Hence,  with  the  aid  of  the 
following  table  of  prices,  the  approximate  cost  of  the  whole  build- 
ing can  be  very  quickly  estimated. 


GENERAL  DESIGN. 


TABLE   OP  APPROXIMATE   PRICES. 

Common  brick  work 25  to*  35c.  per  cu.  ft. 

Rubble  masonry $5  to  $7  per  cu.  yd. 

Concrete $6  to  $8  per  cu.  yd. 

Cut  Stone  pier  caps $2  per  cu.  ft. 

Piles  in  place 25  cts.  per  lin.  ft. 

Earth  excavation 50  cts.  per  cu.  yd. 

Steel  truss  and  column  frame  in  place 4  cts.  per  Ib. 

Steel  beams,  in  place 3 

Plain  casting 2    "      "     " 

Corrugated  iron  No.  22,  in  place,  black 7  cts.  per  sq.  ft. 

"  "          "          "  galvanized 9    "       "         " 

Flashing,   galvanized 15    "     •  "         " 

Spruce  lumber,  in  place  on  floor  or  roof $25  per  M. 

H.  P.  matched,  in  place $35       " 

H.  P.  joist  and  purlins,  on  floor  or  roof $30      " 

Door  frames   and   doors 50  cts.  per  sq.  ft. 

Window  frames  and  windows 50    ' 

Sash,  glazed  and  painted 15  to  25 ' 

Gutter  and  conductor 25  cts.  per  lin.  ft. 

Stairs,  3  ft.  wide,  wood $3  per  step. 

Stairs,  3  ft.  wide,  iron $8  per  step. 

Rolling  steel  shutters 50  cts.  per  sq.  ft. 

Louvres,  fixed 50 

Louvres,    moving 75 

Corrugated  iron  doors  and  shutters 35 

Wire  netting,    galvanized 20 

Skylight,  1/4- in.   thick  glass 25 

Skylight,  translucent  fabric 15 

Pipe  railing 50  cts.  per.  lin.  ft. 

Round  ventilators $5  to  $10  each. 

Metal  cornice 10  to  25  cts.  per  lin.  ft. 

Slate  roof,  not  including  boards $7  to  $12  per  sq.  of  10  x  10  ft. 

Slag  and  gravel  roof,  not  includ'g  boards.  $5  $7 
Prep'r'd  comp'sit'n  roof,  n't  incl'd'g  b'ds  $2  $5 
Wood  shingle  roof,  not  including  boards.  $3  $5 
Tin  plate  roof,  not  including  boards.  . .  .$10  $12 
Corrugated  iron  roof $7  $9 

Roughly  speaking,  the  cost  of  one-story  iron  buildings,  complete, 
is,  for  sheds  and  storage  houses,  40  to  60  cts.  per  sq.  ft.  of  ground, 
and  for  such  buildings  as  machine  shops,  foundries,  electric  light 
plants,  that  are  provided  with  traveling  cranes,  the  cost  is  from  60 
to  90  cts.  per  sq.  ft.  of  ground  covered. 


l6  MILL     BUILDING     CONSTRUCTION. 


CHAPTER  III. 
DESIGN     OF    STRUCTURAL     DETAILS. 

FOUNDATIONS  AND  ANCHORAGE.— The  subject  of  foun- 
dation construction  is  such  an  extensive  one  that  it  is  impossible  to 
consider  it  exhaustively  within  the  limits  assigned  to  this  book. 
It  will  be  evident  to  all,  however,  that  the  design  of  foundations 
for  the  great  majority  of  shop  buildings  is  not  a  difficult  problem, 
since  the  site  selected  for  them  will  usually  be  in  a  location  free 
from  water  and  treacherous  soils. 

For  the  outside  lines  of  columns  either  a  continuous  foundation 
wall,  if  the  columns  are  close  together,  or,  individual  piers,  if  the 
columns  are  widely  separated,  may  be  employed.  In  either  case 
the  foundations  must  have  ample  area  to  distribute  the  loads  over 
a  sufficient  area  of  foundation  bed  to  ensure  safety  from  settlement. 
The  bearing  power  of  different  soils  is  given  in  Table  V. 

If  the  building  is  large  and  any  doubt  exists  as  to  the  nature  and 
quality  of  the  foundation  soil,  soundings  should  be  made  and  the 
bearing  power  tested  by  placing  weights  on  a  small  known  area. 
The  bottom  of  the  walls  should  always  be  carried  to  a  sufficient 

TABLE  V. — Showing  Supporting  Power  of  Various  Foundation  Soils  in  Tons  per 

Square  Foot. 

Bedrock  (hardest) 200 

(poor) 5  to  30 

Dry  clay  in  thick  beds 4 

Soft  clay 1 

Gravel  and  sand  well  cemented 8 

Compact   sand 4 

Clean  and  dry  sand 2 

Quicksand  and  soft  soils .' % 

depth  to  make  certain  that  the  original  bed  soil  is  reached.  A  few 
layers  of  wet  sand  or  gravel  placed  in  the  bottom  of  the  excava- 
tion, filling  it  from  side  to  side,  and  thoroughly  rammed  will  help 
to  distribute  the  pressure  evenly.  The  wall  or  piers  should  have 
two  good  footing  courses  and  the  projection  of  each  course  beyond 
the  one  immediately  above  should  be  so  small  that  the  lower  foot- 
ing will  not  be  cracked  by  the  bending  strain  from  the  load  above. 
Each  column  should  rest  on  a  cut  stone  cap  except  where  the  load 
is  so  small  that  the  foot  of  the  column  may  rest  directly  on  the  reg- 
ular masonry  without  danger  of  crushing.  The  usual  safe  load  for 


GROUND  FLOOR  CONSTRUCTION.  ij 

stone  is  250  Ibs.  per  sq.  in.  and  for  brick  is  125  Ibs.  per  sq.  in.  In 
the  opinion  of  the  writer  hard  brick  or  concrete  .are  superior  to 
stone  for  small  foundations  on  account  of  their  better  bond. 

For  very  light  loads  a  wooden  box  may  be  set  in  the  ground  and 
filled  with  concrete,  the  column  base  resting  directly  on  the  con- 
crete or  on  a  thin  layer  of  cement  mortar  covering  the  top  of  the 
concrete.  In  special  cases  of  heavy  loads  on  soft  soil  a  grillage  of 
concrete  and  I-beams  or  of  concrete  and  railway  rails  will  enable 
the  load  to  be  distributed  over  the  requisite  area  with  a  saving  over 
masonry. 

Where  there  is  a  tendency  toward  overturning,  the  column  bases 
should  be  anchor-bolted  to  the  foundation  masonry.  Generally  the 
anchor  bolts  should  extend  through  the  masonry  and  be  fastened 
on  the  underside.  These  bolts  are  set  in  position  by  means  of 
wooden  templates  and  the  masonry  is  built  up  around  them.  In 
some  cases  a  small  plug  anchor  set  in  the  capstone,  with  sulphur 
or  lead,  will  provide  sufficient  anchorage. 

It  is  the  practice  of  the  writer  in  designing  wall  columns  for 
buildings  to  consider  the  same  rigidly  fixed  at  the  base,  provided 
there  is  sufficient  load  on  the  column  to  hold  it  down.  In  some 
cases  even  though  the  load  may  be  considerable,  if  the  post  is  small 
there  is  still  a  liability  to  pin  ended  action. 

GROUND  FLOOR  CONSTRUCTION. 

CONCRETE  FLOORS.— In  the  construction  of  floors  as  in 
other  parts  of  the  building  the  requirements  of  each  case  will  de- 
termine the  design  and  construction  to  be  adapted.  A  very  solid 
floor  is  made  as  follows:  The  soil  is  excavated  to  a  depth  of 
about  18  ins.  and  leveled  up. 

4Cemen+\     8  Concrete-. 

Upon  the  bottom  of  this  exca- 
vation is  placed  a  6-in.  layer  of 
broken  stone  which  is  thor-  __ 

6  Broken  Sf-one--' 

oughly  rammed  and  then  cov-        Rg   ^    Concrete  Qpound  Roor 

ered  with  a  layer  of  concrete  8  Construction. 

ins.  thick.     After  the  concrete 

has  set  it  is  covered  with  a  wearing  surface  of  cement  4  ins.  thick. 

A  combination  of  asphalt,  Portland  cement  and  sand  makes  a  good 

wearing  surface.    Fig  11  shows  a  section  of  this  floor. 

ASPHALT  FLOORS.— Asphalt  floors  are  becoming  very  popu- 
lar where  small  cost  is  not  the  chief  consideration.  Rock  asphalt 
is  limestone  impregnated  with  from  8$  to  17$  of  bitumen.  It  is 


jg  MILL     BUILDING     CONSTRUCTION. 

found  in  many  localities,  but  the  principal  workable  deposits  are  at 
Limmer  in  Germany,  Neuchatel  in  Switzerland,  and  at  Seyssel  in 
France.  Less  well-known  deposits  exist  at  Ragusa  in  Sicily,  near 
Santa  Barbara  in  California,  and  in  Kentucky,  Colorado,  Utah  and 
New  Mexico.  For  shipping  the  rock  is  usually  made  into  asphalt 
mastic  in  the  following  manner :  The  rock  is  ground  into  powder 
and  heated  in  kettles  with  8$  of  Trinidad  asphaltum  added  to  pre- 
vent burning.  The  mixture  is  heated  to  a  temperature  of  350°  and 
kept  at  that  temperature  for  about  five  hours,  being  constantly 
stirred  the  whole  time.  The  next  step  of  the  process  is  to  mold  the 
mixture  into  blocks  weighing  from  50  Ibs.  to  60  Ibs.  each.  These 
blocks  as  purchased  in  the  market  always  have  the  name  of  the 
mine  from  which  they  come  plainly  stamped  on  them.  When  mar- 
keted the  mastic  should  contain  14$  of  bitumen  and  86$  of  caroon- 
ate  of  lime. 

To  prepare  the  mastic  for  flooring  it  is  mixed  with  Trinidad  as- 
phalt and  sand  in  the  following  proportions  :  Mastic  blocks,  broken, 
I'tephaH-  60  Ibs. ;  Trinidad  asphalt,  4  tbs. ;  fine  gravel  and 

sand,  36  Ibs.  This  mixture  is  heated  for  about 

4'Ccncrefr-'  five  hours  at  400°  F.,  and  is  constantly  stirred 

Rg.  12.  during  the  heating.    At  the  termination  of  this 

Asphalt  Floor  with  Con-  heating  the  material  is  taken  out  of  the  kettles 

crete  Foundation. 

and  spread. 

For  a  mill  floor  the  asphalt  should  be  spread  I  in.  thick  on  a 
foundation  of  concrete  or  on  boards.  The  concrete  foundation 
should  be  3  ins.  or  4  ins.  thick,  and  if  boards  are  used  they  should 
be  covered  with  a  layer  of  sheathing  paper  before  the  asphalt  is 
placed.  Fig.  12  is  a  section  of  asphalt  floor  having  a  concrete  foun- 
dation and  Fig.  13  is  a  similar  section  with  a  foundation  of  wood. 

Any  composition  of  coal  tar  becomes  useless  in  a  short  time  on 
account  of  the  evaporation  of  the  tar  which  causes  the  material  to 
disintegrate   and    crumble    away.     Felt  satu-         MsphaH-*     a^  T. 
rated  with  coal  tar  becomes  brittle  and  finally  f/*m*    m 

useless.    The  oils  of  asphalt,  however,  are  not 
volatile  at  any  natural  temperature,  and  hence    ^^  ^  ^  ^ 
properly  prepared  asphalt  flooring  compos  Foundation, 

tion  remains  absolutely  unchanged  during 
years  of  exposure  to  the  air  and  sunlight.  Other  important 
advantages  of  asphalt  for  flooring  are  that  it  is  impervious  to  water 
and  is  so  elastic  that  cracks  do  not  develop.  An  asphalt  floor  has 
no  joints  to  accumulate  dirt  and  can  be  easily  and  thoroughly 
cleaned.  It  is  pleasant  to  walk  on,  not  tiring  the  feet  as  do  stone 


GROUND    FLOOR 


blocks  or  flagging.  It  is  not  worn  away  by  traffic  as  are  stone 
blocks,  but  is  simply  compressed.  Asphalt  flooring  costs  16  cts. 
per  square  foot  when  laid  i-in.  thick,  the  cost  running  higher  or 
lower  according  to  the  location  and  size  of  the  floor. 

There  are  many  imitations  of  asphalt  made  of  coal  tar  and 
crushed  limestone  which  it  is  almost  impossible  to  distinguish  from 
the  genuine  article,  but  none  of  these  imitations  has  the  properties 
of  asphalt.  These  imitation  asphalts  will  all  crack  and  crumble 
after  a  few  years'  service. 

Asphalt  is  softened  and  finally  destroyed  by  oil  and  it  cannot, 
therefore,  be  recommended  for  floors  subjected  to  oil  drippings 
from  machinery  and  materials. 

WOOD  FLOORS.— A  first-class  wood  floor  is  made  as  follows : 
Excavate  the  soil  to  a  depth  of  18  ins.  and  place  a  thoroughly 
rammed  layer  of  concrete  8  ins.  thick  on  the  bottom.  After  this 
layer  of  concrete  has  set  place  6x6-in.  sleepers  of  pine  or  spruce  3 

ft.  apart  c.  to  c.  and  fill  be- 
tween them  and  flush  with 
their  tops  with  a  second  layer 
of  concrete.  For  a  wearing 


3'Plank- 


m 


® 


14. 


Heavy  Timber  and  Concrete 
Floor. 


surface  lay  a  flooring  of  3-in. 

plank  spiked  to  the  sleepers. 

Fig.  14  is  a  section  of  floor  of 

this  construction.  This  floor  construction  is  heavy  and  solid  and 
will  carry  ordinary  machinery  without  special  machine  founda- 
tions. 

A  much  lighter  and  cheaper  wood  floor  may  be  constructed  by 
embedding  3~in.  plank  or  half-round  sleepers  in  a  layer  of  6  ins. 
or  8  ins.  of  cinders  and  spiking  to  them  a  flooring  of  3~in.  plank 
(Fig.  ^15).  When  this  con- 
struction  of  floor  is  used  all 
machines  must  be  provided 
with  special  foundations. 
Wood  block  pavement  on  a 

concrete  foundation  is  a  form  of  shop  floor  which  has  been 
considerably  used,  but  the  writer  cannot  recommend  this  construc- 
tion. 

FLOOR  FOR  CAR  SHEDS.— Car  sheds  for  electric  railways 
require  a  special  floor  construction  because  of  the  pits  beneath  the 
tracks  for  the  use  of  the  inspectors  and  cleaners.  These  pits  are 
from  4  ft.  to  5  ft.  deep.  A  common  construction  is  to  build  brick 


Fig.  15.  Light  Timber  and  Concrete  Floor. 


20  MILL     BUILDING     CONSTRUCTION. 

piers  nearly  to  the  height  of  the  floor  level  which  carry  timber  sills, 
to  which  the  floor  planking  is  spiked. 

Where  wood  floors  are  employed  the  preservation  of  the  timber 
from  decay  is  an  important  consideration.  The  best  authorities  on 
the  question  recommend  the  application  of  a  coating  of  lime  H-in. 
thick  around  the  sills  and  on  the  bottoms  of  the  floor  planks.  This 
protection  should  give  the  floor  a  life  of  50  years.  Mixing  coal 
tar  with  the  concrete  makes  a  good  preservative,  or  the  concrete 
may  be  covered  with  tar  wherever  the  floor  timbers  come  in  contact 
with  it.  Coating  the  sills  and  the  underside  of  the  planking  with 
rosin  is  another  excellent  means  of  preventing  decay. 

UPPER  FLOOR  CONSTRUCTION. 

STEEL  TROUGH  FLOORS.— There  is  probably  no  more  sub- 
stantial a  construction  for  floors  above  the  ground  floor  than  the 
riveted  steel  trough  construction  known  as  the  Lindsay  floor. 
With  this  construction  the  floor  boards  may  be  laid  directly  on 
the  metal  or  they  may  be  spiked  to  small  timber  sills  embedded 
flush  in  a  concrete  or  cinder  filling  carried  by  the  troughs,  as  shown 
by  Fig.  16.  The  "Hand  Books"  published  by  most  of  the  rolling 
mills  give  the  safe  load  per  square  foot  of  trough  flooring  for  vari- 
ous spans. 

CORRUGATED  IRON  AND  BRICK  ARCH  FLOORS.— A 
cheaper  construction  of  iron  floor  than  the  steel  trough  consists  of 
corrugated  iron  arches  sprung  between  I-beams  and  filled  above 
with  concrete  in  which  the  timber  sills  are  bedded  and  planked  over, 
as  shown  by  Fig.  17.  This  floor  has  no  spring.  Corrugated  iron 
sheets  of  No.  18  B.  W.  G.,  having  a  span  of  6  ft.  and  a  rise  of  10 
ins.,  have  in  actual  tests  sustained  a  load  of  1,000  Ibs.  per  square 
foot.  Brick  or  terra  cotta  arches  filled  above  with  concrete  is  a 
floor  construction  which  has  been  much  used,  but  besides  being 
heavy  and  expensive,  this  construction  cannot  be  recommended  for 
floors  which  are  subjected  to  vibration  from  heavy  running  machin- 
ery. Fig.  18  is  a  section  of  brick  arch  floor. 

STEEL  GIRDER  AND  TIMBER  FLOORS.— A  floor  con- 
struction which  has  been  extensively  employed  consists  of  a  timber 
flooring  carried  by  metal  beams  or  girders.  Fig.  19  shows  one 
form  of  this  construction,  which  consists  of  steel  I-beams  spaced 
3  ft.  or  4  ft.  apart  and  capped  with  timbers  to  which  a  flooring  of 
3-in.  or  4-in.  plank  is  spiked.  Another  form  of  this  construction  is 


UPPER     FLOOR    CONSTRUCTION. 


21 


shown  by  Fig.  20,  which  consists  of  built  up  steel  girders  capped 
with  plank  and  carrying  timber  joists  to  which  ftie  plank  flooring 
is  spiked.  In  this  construction  the  girders  are  spaced  from  10  ft. 
to  15  ft.  apart.  Another  form  of  I-beam  and  timber  floor  construc- 
tion which  is  not  much  used  in  this  country  but  which  is  a  very  effi- 


s-Cynders 


Silvers  Flooring 


£ 'Layers  Flooring /Cynders 


5'Planh 
•10'xl?  abort  8'0'C.*>tr~ 

Fig.    20.  Fig.    22. 

Figs.  16  to  22.    Typical  Upper  Floor  Constructions. 

cient  construction  for  heavy  loads  is  shown  by  Fig.  21.  The  I- 
beam  joists  are  spaced  the  proper  distance  apart,  which  should  be 
not  more  than  3  ft.  or  4  ft.,  so  that  the  depth  of  the  wooden  flooring 
may  be  kept  at  the  minimum,  and  on  them  planks  are  set  close  to- 
gether on  edge  and  firmly  spiked  together.  The  top  of  this  plank- 
ing is  then  covered  with  a  J-in.  coating  of  fine  sand  mortar  and 
a  wearing  surface  of  matched  boards  is  laid  on  top  of  it. 

SLOW  BURNING  WOOD  FLOORS.— A  form  of  floor  con- 
struction known  as  "slow  burning  construction"  is  shown  by  Fig. 
22.  The  principle  of  this  construction,  which  is  entirely  of  wood, 
is  to  concentrate  the  timber  into  the  fewest  number  of  large  pieces 
so  that  a  minimum  surface  will  be  exposed  to  the  attack  of  flames. 
The  construction  consists  simply  of  widely  spaced  heavy  timber 
joists  covered  with  a  flooring  of  heavy  planks. 


22  MILL     BUILDING     CONSTRUCTION. 


ROOF  COVERINGS 

GENERAL  CONSIDERATIONS.— The  importance  of  having 
an  absolutely  weather-proof  roof  for  shop  buildings  is  evident  with- 
out argument.  The  kind  of  roof  covering  employed  determines 
in  a  large  measure  the  possible  pitch  or  slope  of  the  roof.  A  roof 
with  a  steep  slope  sheds  rain  and  snow  more  efficiently  than  one 
which  is  more  nearly  flat,  but  it  has  the  disadvantage  of  a  greater 
area  and  consequently  of  being  heavier  and  also  of  presenting  a 
larger  surface  to  wind  pressure.  All  metal  roofs  are  lightning- 
proof  and  because  of  their  smooth  surfaces  are  more  easily  kept 
clean  by  the  wind  and  rain  and  the  rainwater  from  them  is  likely  to 
be  more  pure  than  that  off  a  shingle  or  gravel  roof.  With  these 
brief  general  remarks  attention  will  be  turned  to  the  various  forms 
of  roof  coverings. 

SLATE  ROOFING.— Roofing  slates  are  usually  from  -J-in.  to 
J-in.  thick  and  of  various  sizes.  The  minimum  slope  of  roof  rec- 
ommended for  slate  covering  is  one  with  a  6-in.  pitch.  If  the  pitch 
is  less  than  this  water  is  likely  to  be  driven  through  the  joints  in 
beating  rains.  If,  however,  the  joints  are  laid  in  cement,  the  pitch 
may  be  decreased  to  4  ins.  or  5  ins.  to  the  foot.  Cement  joints  are 
advantageous  in  any  case  since  they  prevent  the  slates  from  break-, 
ing  and  make  the  building  warmer  in  winter  and  cooler  in  summer. 
A  few  courses  of  slate,  with  cement  joints,  are  always  advisable  at 
the  eaves  and  ridges  and  around  chimneys.  If  the  roof  is  exposed 
to  the  action  of  the  corrosive  gases,  as  is  the  case  in  chemical  works, 
cement  joints  are  imperative  because  any  kind  of  nails  will  be  de- 
stroyed after  a  time. 

Slate  when  well  laid  have  a  longer  life  probably  than  any  other 
form  of  roof  covering;  they  will  last  for  50  years  or  more.  Slate 
make  a  fire-proof  roof  covering,  but  they  will  crack  when  exposed 
to  heat  and  also  if  they  are  walked  upon.  Hard  slate  of  a  shiny  ap- 
pearance are  the  best;  those  that  absorb  water  will  be  destroyed 
by  frost.  Slate  may  be  laid  on  boards,  on  lath  or  directly  on  iron 
purlins.  When  laid  on  wood  they  are  held  in  place  by  two  nails, 
one  in  each  upper  corner.  When  laid  on  iron  purlins  they  are  held 
in  place  by  copper  wire.  For  roofs  of  small  pitch  a  lining  of  roof- 
ing felt  will  help  to  make  the  roof  watertight. 


ROOF     COVERINGS.  2^ 

The  cost  of  nails  for  slate  roofing  varies  with  the  market,  but  the 
following  table  is  a  fair  average : 

3d.  galvanized  slate  nails,  per  keg $5.50 

4d.          ••  "  '     "       5.00 

3d.  tinned  "  "       5.75 

4d.        "  ««  ««       5.25 

3d.  or  4d.  polished  steel  wire  nails,  per  keg 4.00 

Copper  nails,   per  Ib 20 

Slaters'  felt  in  rolls  of  six  squares  costs  $1.25  per  roll;  two-ply 
tar  roofing  felt  costs  $i  per  square,  and  three-ply  $1.25  per  square. 
Slaters'  cement  in  25-lb.  kegs  costs  10  cts.  per  pound. 

Shorter  slates  must  be  used  for  the  first  course  at  the  eaves 
and  the  final  course  at  the  peak.  To  give  the  first  course  at  the 
eaves  the  same  inclination  or  slope  that  the  succeeding  courses  will 
have,  a  thin  lath  must  be  laid  under  the  slate  at  the  edge  of  the 
eaves.  A  lap  of  3  ins.  is  the  amount  usually  allowed  and  it  should 
not  be  decreased.  Slate  does  not  make  a  cheap  roof  covering,  be- 
cause it  is  heavy  and  requires  a  stronger  framing  to  carry  it,  and  be- 
cause the  steep  pitch  required  makes  the  area  to  be  covered  large. 
At  present  the  Brownville  and  Monson  slates  of  Maine  and  the 
Peach  Bottom  slate  of  Pennsylvania  are  the  best  and  also  the  most 
expensive. 

The  weight  of  slate  per  cubic  foot  is  174  Fbs.,  hence  the  weight 
per  square  foot  of  different  thicknesses  of  roofing  slate  is  as  fol- 
lows: 

Weight,  IDS.  Weight,  Ibs. 

Thickness.              per  sq.  ft.  Thickness.            per  sq.  ft. 

Vs-ln.                      1.81  Vs-in.                      5.43 

Vie-in.                     2.71  V2-in.                     7.25 
V*-in.                     3.62 

An  experienced  roofer  will  lay  about  two  (10  ft.  x  10  ft.)  squares 
per  day  of  ten  hours.  The  price  of  the  best  slate  on  board  cars  at 
the  quarries  is  from  $5  to  $7  per  square,  according  to  size  and  color. 
Red  slate  costs  from  $10  to  $12  per  square,  and  ordinary  slate, 
black,  purple,  or  of  mixed  colors,  cost  from  $2  to  $4  per  square. 
These  prices  include  punching  and  countersinking  the  nail  holes. 
Table  VI.  gives  the  number  of  slate  per  square,  using  3-in.  lap  for 
various  sizes  of  slate. 

TABLE  VI.— Showing  Number  of  Roofing  Slate  of  Different  Sizes   and  3-in.   Lap 

Required  per  Square  of  10  x  10  ft. 

Size,  No.  in  each  Size,  No.  in  each          Size,  No.  in  each 

ins  square  laid.  ins.  square  laid.  ins.  square  laid. 

6xi2  533  9x16  247  11x22  138 

7x12  457  10x16  222  12x22  126 

8x12  400  9x18  214  12x24  115 

7x14  374  10x18  192  13x24  106 

8x14  327  10x20  170  14x24  98 

9x14  291  11x20  154 

8x16  277  12x20  142 


24  MILL     BUILDING     CONSTRUCTION. 

ASPHALT  ROOFING.— Asphalt  roofing  for  flat  roofs  is  ap- 
plied as  follows :  (i)  One  or  two  layers  of  felt  paper;  (2)  a  coating 
of  asphalt  roofing  cement;  (3)  a  layer  of  roofing  felt;  (4)  a  final 
coating  of  asphalt  cement  into  which  is  rolled  clean  sand  and  fine 
gravel.  For  pitched  or  sloping  roofs  the  layers  of  roofing  felt  al- 
ready cemented  together  by  the  first  coating  of  asphalt  cement  are 
sold  in  rolls  about  36  ins.  wide.  This  covering  is  laid  in  courses 
with  the  edges  overlapping  about  2  ins.  and  fastened  with  the  nails 
and  tin  washers.  When  laid  the  roofing  is  covered  with  the  final 
coating  of  asphalt  cement  and  gravel.  A  canvas  bottom  layer  may 
be  used  in  place  of  the  first  layer  of  paper.  This  form  of  covering, 
with  the  top  covering  and  gravel  complete  and  ready  for  laying 
is  sold  for  $3.50  per  square  of  10x10  ft. 

The  principal  advantage  of  any  kind  of  asphalt  roof  covering  is 
that  it  is  perfectly  water-proof,  and  after  being  laid  it  does  not 
crack  or  peel  off  like  tar  and  does  not  run  at  any  natural  tempera- 
ture. When  graveled  over  it  makes  a  practically  fire-proof  roof- 
ing. Finally,  it  is  easily  applied  by  unskilled  workmen. 

SLAG  AND  GRAVEL  ROOFING.— Slag  is  preferable  to 
gravel  for  these  roofs  because  of  its  lighter  weight.  The  construc- 
tion of  both  slag  roofing  and  gravel  roofing  is  as  follows :  (i)  Three 
layers  of  felt  paper  are  fastened  to  the  roof;  (2)  a  coating  of  tar  is 
applied  to  the  top  layer  of  felt ;  (3)  two  layers  of  felt  paper  are  laid 
on  the  tar;  (4)  a  covering  of  tar  is  applied  to  the  top  layer  of  the 
second  course  of  felt  using  about  eight  gallons  of  tar  per  10x10  ft. 
square,  and  the  slag  or  gravel  is  rolled  into  the  tar.  This  form  of 
roof  covering  should  last  from  10  to  20  years.  It  is  fire-proof, 
needs  no  paint  and  refracts  the  heat.  It  is  noiseless  and  is  not  af- 
fected by  gas,  acids,  etc.  Finally,  it  is  a  comparatively  cheap  cover- 
ing, costing  50$  less  than  tin. 

CORRUGATED  IRON  ROOFING.— Corrugated  iron  is  made 
from  sheet  iron  of  standard  gages  by  stamping,  one  corrugation 
being  stamped  at  a  time.  As  there  are  no  sharp  joints  to  be  made 
there  is  no  advantage  in  using  sheet  steel.  The  corrugated  sheets 
are  made  in  lengths  increasing  in  dimensions  by  even  feet  from  5 
ft.  to  10  ft.,  inclusive,  and  of  such  width  that  they  lay  2  ft.  even  on 
the  roof.  The  sizes  of  corrugations  made  in  the  United  States 
are  5  ins.,  2.\  ins.,  \\  ins.,  f-in.,  and  3-i6-in.  c.  to  c.  of  corrugations. 
The  2j-in.  corrugation  is  the  size  most  commonly  used.  Table 
VII.  gives  the  costs  and  weights  of  both  black  and  galvanized  iron 


ROOF     COVERINGS. 


for  Birmingham  Wire  Gage  and  the  new  American  Standard  Gage 
adopted  by  Congress  in  i< 


TABLE  VII.— Showing  Cost  and  Weight  per  10  x  10  ft.   Square  of  Painted  and 
Galvanized  Corrugated  Iron. 

1 American. \ 

i —  Painted.  — |     (-Galvanized. -| 
Wt.lbs.    Price    Wt.lbs.     Price 
per  sq.     per  sq.  per  sq.  per  sq. 
$2.90         86        $4.90 


i  Birm 
j—  Painted.—  |  ,- 
Wt.lbs.  Price  "^ 
Gage,    persq.  persq. 
28...  

ingham 
—  Galva 
Vt.lbs. 
persq. 
81 
94 
101 
114 
141 
188 
221 
287 

nized.  —  | 
Price 
per  sq. 

$5!40 
5.60 
5.80 
6.80 
8.40 
11.60 
15.20 

27. 
26. 
24. 
22. 
20. 
18. 
16. 

72 
81 
98 
123 
153 
214 
283 

$3.00 
3.20 
3.80 
4.60 
5.40 
7.20 
9.60 

77 
84 
111 
138 
165 
220 

3.10 
3.30 
4.15 
4.90 
5.80 
7.40 
8.60 

93 
99 
127 
154 
182 
236 

$5.30 
5.50 
6.40 
7.40 

The  prices  given  in  Table  VII.  are  for  small  lots ;  for  car  load  lots 
the  prices  will  be  about  10$  less.  This  table  also  refers  to  5-in.  2.\- 
in.,  and  3-i6-in.  corrugations ;  for  i  J-in.  and  f-in.  corrugations,  5$ 
should  be  added  to  the  weights  and  prices  given.  If  painted  with 
asphalt  or  graphite  instead  of  iron  oxide,  the  cost  will  be  25  cts.more 
per  10x10  ft.  square.  Wire  nails  cost  10  cts.  per  square;  galvan- 
ized nails  cost  15  cts.  per  square  and  cleats  and  bolts  cost  25  cts. 

per  square.    The  price  of  curved  sheets 
is  20%  more  than  that  of  straight  sheets. 
The  sheets  of  corrugated  iron  should 
be  laid  with  a  lap  of  4  ins.,  as  shown  by 
Fig.  23,  when  used  for  covering  side 
Fig.S4.  walls,  and  with  a  lap  of  6  ins.,  as  shown 

by  Fig.  24,  when  used  for  roof  covering. 

When  laid  on  wood  sheathing  corrugated  iron  covering  is  lined 
with  water-proof  paper  and  fastened  with  6d.  nails,  using  about  25 
nails  per  sheet.  When  laid  on  iron  purlins  for  boiler  houses  or 
anywhere  that  water  is  likely  to  collect  on  the  underside  of  the  cor- 
rugated sheets,  a  lining  of  the  following  composition  may  be  em- 
ployed: (i)  Wire  netting  tightly  stretched  over  the  purlins;  (2) 
asbestos  paper;  (3)  tar  paper;  (4)  asbestos  paper;  (5)  tar  paper;  and 
(6)  the  corrugated  iron  roof  covering.  When  corrugated  iron  is 
laid  over  iron  purlins  it  may  be  fastened  to  them  by  clinch  nails 
bent  around  the  purlins,  as  shown  by  Fig.  25,  or  by  cleats  of  f-in. 
hoop  iron  2\  ins.  long  riveted  or  bolted  to  the  sheets  and  to  the  pur- 
lins. Generally,  however,  cleats  of  this  form  are  used  especially 
with  channel  or  Z-bar  purlins.  The  clinch  nails  or  cleats  should  be 
placed  about  5  ins.  or  6  ins.  apart  and  care  should  be  taken  to  con- 


26  MILL     BUILDING     CONSTRUCTION. 

nect  them  always  to  the  tops  of  the  corrugations,  as  shown  by  Fig. 
25.     The  following  table  shows  the  size  of  clinch  nails  to  be  used 


Fig.  25.    Clinch  Nail  Fastening  for  Corrugated  Iron  Roofing. 

with  different  sizes  of  angle  purlins  and  also  the  number  of  nails 
to  the  pound  in  each  instance : 

Purlin    angle 2  x  2  ins.    2^x3  ins.    3%  x  3^  ins.    4x4^  ins. 

Length  of  nail 4  ins.  5  ins.  6  ins.  7  ins. 

No.  of  nails  per  Ib.  .        48  38  33  27 

Corrugated  iron  of  No.  27  and  No.  28  gage  is  too  thin  to  sup- 
port any  weight  above  and  must  be  laid  over  sheathing.  For  other 
gages  the  purlin  spacing  should  be  as  follows : 

Thickness,  Spacing  c.  to  c.,  Thickness,  Spacing  c.  to  c., 

B.  W.  G.  ft.        ins.  B.  W.  G.  ft.        ins. 

No.  26 2  0  No.  20 4          0 

"24 2  6  "18 5          0 

"22 3          0  "16 6          0 

The  advantage  of  galvanized  over  black  corrugated  iron  is  that 
it  requires  painting  less  frequently.  Galvanized  corrugated  iron 
seldom  needs  to  be  painted  within  five  or  six  years  after  erection. 
When  painting  becomes  desirable,  it  is  always  necessary  to  remove 
the  zinc  by  applying  with  a  brush  the  following  wash :  Chloride  of 
copper,  one  part ;  nitrate  of  copper,  one  part ;  and  salammoniac,  one 
part,  dissolved  in  64  parts  of  water,  with  one  part  hydrochloric  acid 
added  to  the  solution.  This  solution  will  burn  the  metal  black 
ready  to  receive  paint  in  about  24  hours.  Black  corrugated  iron 
should  be  painted  upon  leaving  the  shop  and  about  every  two  years 
thereafter. 

Corrugated  iron  is  not  recommended  for  roofs  having  a  slope  of 
less  than  3  ins.  in  12  ins.,  and  if  it  is  used  for  flatter  roofs  all  the 
joints  should  be  laid  in  elastic  cement.  Cement  joints  can  be  used  to 
advantage  for  roofs  of  any  pitch  since  they  ensure  a  much  tighter 


ROOF     COVERINGS.  27 

covering.  When  corrugated  iron  is  used  for  siding  where  it  is  lia- 
ble to  receive  shocks,  a  heavy  gage  should  be  employed.  The  sid- 
ing should  not  touch  the  ground  as  contact  with  the  earth  hastens 
its  corrosion. 

SHEET  STEEL  ROOFING.— Sheet  steel  is  a  cheap  roof  cover- 
ing ;  it  is  light  and  water  tight  and  as  it  comes  in  large  sheets  it  can 
be  rapidly  applied ;  it  is  suitable  for  roofs  of  any  pitch,  is  lightning 
proof  and  has  a  low  insurance  rate.  Sheet  copper,  sheet  lead  and 
sheet  zinc  have  been  used  for  roofing  in  special  cases,  but  they  are 
much  more  expensive  than  sheet  steel. 

Sheet  steel  roofing  is  annealed  Bessemer  steel  of  the  best  qual- 
ity ;  a  sample  piece  may  be  hammered  into  all  kinds  of  shapes  with- 
out cracking.  Sheet  iron  is  unsuitable  for  roofing  since  it  is  liable 
to  break  when  bent  and  hammered  to  a  flat  joint.  Sheet  steel  roof- 
ing should  not  be  laid  over  tar  paper  or  on  wood  containing  acids, 
and  it  should  have  a  coat  of  paint  on  top.  Steel  roofing  sheets  are 
made  96x28  ins.  in  size  and  will  cover  an  area  93^x24  ins.  They 
must  be  laid  over  lath  or  sheathing,  and  if  warm  air  comes  into  con- 
tact with  the  undersides  of  the  sheets  they  should  be  protected  by 
an  anti-condensation  lining  of  the  construction  used  for  corrugated 
iron  roofing  previously  described,  or  by  a  lining  of  asbestos  paper. 

The  weight  of  sheet  steel  roofing  of  the  construction  just  de- 
scribed is  about  80  Ibs.  per  10x10  ft.  square.  At  present  prices  the 
cost  per  square  of  No.  27  B.  W.  G.  sheet  steel  painted  red  is  $3.50, 
and  of  galvanized  sheet  steel  is  $5.90.  These  prices  are  for  small 
lots ;  for  car  load  lots  the  cost  will  be  about  10$  less.  Graphite 
paint  costs  25  cts.  more  per  square  than  iron  oxide  paint.  Table 
VIII.  shows  the  weight  per  square  foot  of  painted  and  galvanized 
steel  roofing  sheets  of  different  gages.  Roughly  speaking,  galvan- 
ized sheets  weigh  about  20  Ibs.  per  10x10  ft.  square  more  than  black 
or  painted  sheets. 

TABLE  VIII.— Showing  Weight  in  Lbs.   per  Square  Foot  of  Steel  Roofing  Sheets 

of  Different  Gages. 

r Gage. 1 

Gage.  27   26   24   22   20   18  .  16 

B.  W.  G Black     64      .72      .88    1.12    1.40    1.97    2.60 

B.  W.  G Galvanized  ..     .88      .94    1.06    1.31    1.75    2.06    2.69 

U.  S.  Standard,  Black     .68      .75    1.0      1.25    1.50    2.00    2.50 

U.  S.  Standard,   Galvanized    .  .   .84      .90    1.16    1.41    1.66    2.16    2.66 

CRIMPED  ROOFING.— Crimped  roofing  is  laid  directly  on 
wood  rafters  or  over  sheathing,  the  latter  construction  being  pref- 
erable, and  is  probably  the  least  expensive  metal  roof  covering 


28  MILL     BUILDING     CONSTRUCTION. 

available.  It  should  have  a  pitch  of  at  least  2  ins.  to  the  foot. 
Crimped  roofing  weighs  83  Ibs.  per  10x10  ft.  square  painted,  and 
its  present  cost  for  No.  27  B.  W.  G.  is  $3.10  per  square  painted  and 
$5.50  per  square  galvanized.  For  car  load  lots  10$  should  be  de- 
ducted from  the  above  prices. 

STEEL  ROLL  ROOFING.— Steel  roll  roofing  differs  from 
steel  sheet  roofing  by  having  the  sheets  of  8  ft.  and  10  ft.  length 
joined  at  the  factory  into  a  continuous  piece  some  50  ft.  long.  As 
the  side  joints  must  be  made  after  the  material  is  laid  out  on  the 
roof  this  roofing  is  more  suitable  to  roofs  of  small  pitch,  say  I  in. 
to  the  foot,  than  to  steeper  roofs.  Steel  roll  roofing  is  easily  han- 
dled and  the  cost  of  shipping  is  less  than  in  the  case  of  steel  sheets 
which  have  to  be  boxed.  Parrafined  felt  packing  should  be  in- 
serted in  the  joints.  If  desired  the  manufacturers  will  make  stee! 
roll  roofing  in  any  length  required  up  to  150  ft.  to  suit  the  length 
of  roof  to  be  covered.  This  roofing  weighs  about  85  Ibs.  per  10x10 
ft.  square,  and  in  sheets  of  No.  27  B.  W.  G.  it  costs  $3.50  per  square 
painted,  and  $5.90  per  square  galvanized.  Steel  roll  roofing  re- 
quires no  ridge  capping  since  the  strips  or  rolls  are  continuous  over 
the  ridge.  Generally  the  manufacturers  of  any  kind  of  steel  roof- 
ing having  folded  joints  provide  special  tools  for  laying  it. 

TIN  AND  TERNE  PLATE  ROOFING.— Tin  and  terne 
plate  roofing  are  generally  used  only  for  flat  roofs  or  roofs  with  a 
small  pitch.  The  plates  come  in  I4x2o-in.  and  28x2o-in.  sizes,  and 
well  laid  plates  of  good  quality  should  last  30  years.  It  is  very  im- 
portant to  the  life  of  the  covering  that  its  joints  should  be  well  sol- 
dered and  that  there  should  be  no  travel  on  the  roof.  Tin  and  terne 
plates  may  be  laid  on  sheathing  or  over  old  shingles.  If  the  roof 
is  quite  flat  all  joints  should  be  soldered,  but  when  laid  on  sloping 
roofs  the  side  joints  may  be  folded  and  the  cross  or  horizontal 
joints  soldered.  Some  roofers  lock  all  joints  and  fill  the  horizontal 
seams  with  lead.  The  sheets  are  fastened  to  the  roof  by  cleats; 
if  the  side  joints  are  soldered  the  cleats  should  be  soldered  in  the 
joints.  For  sloping  roofs  it  is  often  convenient  to  have  a  number 
of  sheets  jointed  in  the  shop  into  strips  of  the  right  length  to  reach 
from  the  eaves  to  the  ridge.  After  laying  the  plates  should  be 
painted  with  two  coats  of  paint  and  they  should  be  repainted  about 
every  two  years  afterward.  To  reduce  the  noise,  tin  or  terne  sheet 
roofing  may  be  laid  on  a  lining  of  tar  paper. 

The  old  method  of  preparing  tin  or  terne  plates  was  to  immerse 


ROOF     COVERINGS.  29 

the  sheet  of  iron  or  steel  in  a  bath  of  tin  or  lead,  a  coating  of  which 
adhered  to  the  plates  when  they  were  remove'd.  The  modern 
method  of  manufacture  is  to  pass  the  sheets  between  rolls  which 
are  immersed  in  a  bath  of  tin  or  lead,  and  thus  by  adjusting  the  rolls 
to  secure  a  coating  as  thin  or  as  thick  as  may  be  desired.  The  cost 
of  the  finished  plate  depends  largely  upon  the  thickness  of  the  coat- 
ing. Plates  coated  with  lead  are  called  ternes  and  are  somewhat 
cheaper  and  less  durable  than  tin  plates.  Terne  plates  are  more 
generally  used  for  roofing  than  tin  plates.  The  best  plates  are 
made  from  charcoal  iron,  but  Bessemer  steel  is  also  used.  The 
thickness  of  sheets  commonly  employed  are  known  as  I  C  and  I  X, 
and  correspond  to  No.  30  and  No.  28  B.  W.  G.,  respectively. 

METAL  SHINGLE  ROOFING.— Metal  shingles  are  made 
either  of  tin  or  terne  plate  or  of  sheet  steel  painted.  They  possess 
the  regular  advantages  of  metal  roofing,  being  fire  and  lightning 
proof,  of  light  weight  and  not  being  easily  cracked  or  detached. 
Like  shingles  of  any  kind  they  cannot  be  laid  on  flat  roofs.  They 
are  manufactured  in  a  great  variety  of  sizes  and  forms  to  fit  differ- 
ent kinds  of  sloping  roof,  are  durable  and  present  a  fine  appearance. 
Metal  shingle  roofing  weighs  from  90  Ibs.  to  no  fbs.  per  10x10  ft. 
square. 

RUBBER  ROOFING.— Rubber  roofing  is  made  of  felt  paper 
soaked  in  a  preparation  of  rubber  and  then  rolled.  It  is  put  up  in 
rolls  32  ins.  wide  and  is  laid  lengthwise  of  the  roof  and  fastened 
either  with  strips  running  up  and  down  the  roof  about  2  ft.  apart 
or  with  nails  and  tin  washers.  After  being  laid  the  roofing  is  coated 
with  two  coats  of  slate  paint,  the  upper  coat  of  which  is  sanded. 
Rubber  roofing  is  very  cheap  and  is  especially  suitable  for  tempo- 
rary roofs  or  for  sheds  where  an  expensive  covering  is  not  required. 
When  painted  it  does  not  take  fire  easily,  and  it  can  be  laid  on  roofs 
having  a  pitch  as  flat  as  2  ins.  to  the  foot.  It  does  not  make  a  hot 
upper  story  as  some  other  coverings  do.  The  slate  paint  does  not 
contain  tar  and  so  will  not  crack  or  peel  off,  and  it  is  very  elastic. 
The  color  is  chocolate  brown.  As  usually  laid  the  layers  are  lapped 
about  2  ins.  The  cost  of  rubber  roofing  complete  as  described,  in- 
cluding nails,  painting  and  sanding,  runs  from  about  $2.50  to  $3.75 
per  10x10  ft.  square,  according  to  the  thickness  of  the  felt  paper 
used. 

ASBESTOS  ROOFING.— Asbestos  roofing  is  made  of  canvass 
coated  on  both  sides  with  a  water-proof  composition  and  lined  on 
the  bottom  with  Manilla  paper  and  on  the  top  with  asbestos  felt.  It 


MILL     BUILDING     CONSTRUCTION. 


is  laid  in  horizontal  courses  and  fastened  with  nails  and  tin  washers, 
and  afterwards  it  is  coated  with  asbestos  paint.  Asbestos  roofing 
weights  complete  as  described  about  85  Ibs.  per  10x10  ft.  square 
and  costs  about  $4.50  per  square.  The  covering  requires  occasional 
repainting,  the  paint  costing  from  40  cts.  to  50  cts.  per  gallon  and 
one  gallon  covering  about  100  sq.  ft.  Asbestos  cement  for  stop- 
ping leaks  and  calking  around  chimneys  costs  from  5  cts.  to  10 
cts.  per  pound.  Asbestos  building  felt  in  rolls  36  ins.  wide  weigh- 
ing about  70  Ibs.  per  roll  costs  about  12  cts.  per  pound.  This  paper 
runs  6  Ibs.,  10  Ibs.,  and  14  Ibs.  in  weight  for  thin  medium  and  thick 
paper,  respectively.  Another  paper  made  from  long  fibered  asbes- 
tos costs  about  15  cts.  per  pound. 

WOOD  SHINGLE  ROOFING.— According  to  Kidder's  "Ar- 
chitects' Pocket  book" : 

"The  average  width  of  a  shingle  is  4  ins.  Hence  when  shingles 
are  laid  4  ins.  to  the  weather,  each  shingle  averages  16  sq.  ins.,  and 
900  will  cover  a  square.  If  laid  4^  ins.  to  the  weather,  800  will  cover 
a  square ;  if  laid  5  ins.  to  the  weather,  650  will  cover  a  square ;  and  if 
laid  6  ins.  to  the  weather,  600  will  cover  a  square.  This  is  for  com- 
mon gable  roofs.  In  hip  roofs  where  the  shingles  are  cut  more  or 
less  to  fit  the  roof,  add  $%.  A  carpenter  will  carry  up  and  lay  on  the 
roof  from  1,500  to  2,000  per  day,  or  two  and  a  half  squares  of  plain 
roofing;  1,000  shingles  laid  4  ins.  to  the  weather  will  require  5  Ibs. 
of  shingle  nails." 

When  cost  will  permit  and  the  roof  is  not  steep  shingles  should 
be  laid  in  f-in.  of  mortar,  as  the  lime  prevents  decay.  The  life  of 
shingles  is  greatly  increased  if  they  are  dipped  in  paint  before  being 
laid. 

COMPARATIVE  COST.— The  comparative  approximate  cost 
per  square  of  10x10  ft.  of  the  several  kinds  of  roof  covering  which 
have  been  described  is  given  by  Table  IX. 

TABLE  IX. — Giving  Comparative  Approximate    Cost  per  10  x  10  ft.   Square  of 

Different  Roof  Coverings. 
Slate  on  iron  purlins $2.00  to  $7.00  per  sq. 


Metal  tile,  tin 8.50 

"     steel,  lead-coated    10. 7o 

Rubber  roofing 2.00 

Felt   and    gravel 6.50 

Ornamental  tile 40.00 

Tile  shingles 21.00 

Charcoal  tin  plates,  I.C.,  14  x  20  ins 6.00 

•«  I.e.,  20x28  " 12.00 

I.X.,  14x20  " 7.50 

I.X.,  20x28  "   15.00 

Coke  plates,  tin,  I.C.,  14  x  20  ins 5.50 

"      "        I  C.,  20  x  28  " 11.50 

««      "        I.X.,  14  x  20  "   7.50 

Charcoal  plate,  terne,  I.C.,  14x20  ins..  ..  5.50 
"  I.e.,  20x28  "  ....10.75 
"  I.X.,  14x20  "  ....  6.40 
"  I.X.,  20x28  "  ....12.80 


9.75 
13.75 
3.75 

60.00  per 


M. 


35.00 

6.50  per  box  of  112. 
13.00 

8.50 
17.00 

12.00 


11.00 


MISCELLANEOUS    STRUCTURAL    DETAILS. 


MISCELLANEOUS  STRUCTURAL  DETAILS. 

WALL  ANCHORAGES  OF  ROOF  TRUSSES.— There  are 
several  methods  of  anchoring  roof  trusses  to  the  side  walls  of  build- 
ings. Fig.  26  shows  the  standard  anchorage  in  which  the  lower 
chord  of  the  truss  is  connected  by  bolts  to  the  projecting  end  of  a 
plate  built  into  the  wall  masonry.  Fig.  27  shows  an  anchorage  con- 
sisting of  bolts  set 
into  the  wall  and  at- 
tached to  a  washer 
plate  at  their  bot- 
toms. Fig.  28  shows 
a  similar  anchorage 
with  the  washer 
plate  omitted  and 
the  bolts  held  in  the 
masonry  by  cement. 
Fig.  29  shows  a 
method  of  attaching 
the  truss  to  the  side 
of  the  wall.  As 
shown  by  the  draw- 
ing, the  anchor  bolts 
pass  through  the  wall 
against  the  outside 
of  which  their 'heads 
secure  a  bearing  by 
means  of  a  washer 
plate.  The  area  of 
this  washer  plate  in 


Fig.  30. 


Fig.  27. 


-ZRouqhBol+s 
sef  in  Cement 


Fig.   28. 
Figs.  26  to  32. 


Fig.  32. 


Typical  Wall  Anchorages  for  Roof 
Trusses. 


square  inches  should 
equal  eight  times  the 
tension  on  the  bolts 

in  tons.  It  is  important  also  that  the  end  of  the  truss  should  fit 
tight  to  the  wall,  shims  being  used  if  necessary  to  ensure  such  a 
fit.  The  following  table  shows  the  diameter  of  bolt  to  be  used  for 
walls  of  different  thicknesses;  the  washer  plate  area  in  square 
inches  to  be  allowed  for  each  bolt,  and  the  holding  value  of  the 
bolt  in  tons : 

Diam.,  8-in.  wall,  12-in.  wall,  16-in.  wall,  20-ln.  wall,  Area  of  plate, 

ins.  tons.               tons.               tons.               tons.                 sq.  ins. 

%....  0.5                 0.7                  ...                  ...                     18 

% 0.6                 0.9                 1.0                 ...                     26 

%..  0.7                 1.05               1.4                 ...                     36 

£  0.8                 1.2                 1.6                 1.77                 46 


MILL     BUILDING     CONSTRUCTION. 


When  it  is  inexpedient  to  pass  the  anchor  bolts  through  the  wall, 
as  shown  by  Fig.  29,  the  anchorage  is  accomplished  by  inserting  ex- 
pansion bolts  into  the  wall.  The  following  table  shows  the  holding 
power  of  expansion  bolts  of  different  sizes : 


Diam., 
ins. 


4  ins. 
0.24 
0.28 


-Holding  power  in  tons  for  lengths  of 1 

6  ins.  8  ins.  10  ins.  12  ins. 

0.36  0.46  0.52 

0.42  0.56  0.70  0.84 

0.47  0.65  0.81  0.99 

0.57  0.75  0.93  1.12 


Fig.  30  shows  the  end  of  the  truss  built  into  the  wall,  the  angle 
clips  serving  as  anchors.  Fig.  31  shows  the  method  of  anchoring  a 
beam  built  into  the  wall;  the  length  of  the  rod  should  equal  the 

width  of  the  beam  flange  plus 
6  ins.  Fig.  32  shows  the  man- 
ner of  anchoring  channel  beam 
wall  struts.  The  anchor  bolts 
should  be  spaced  about  3  ft. 
apart.  If  the  struts  are  to  be 
anchored  to  a  wall  already 
built  the  bolts  should  be  run 
through  the  wall  with  washers 
on  the  outside,  or  expansion 
bolts  may  be  used. 


Fig.  33.     Construction  for  Narrow 
Doors. 


DOORS  AND  WINDOWS. 
— Narrow  doors  may  be  made 
without  center  styles  and  wide 
doors  should  have  two  or  more 
spaced  from  3  ft.  to  6  ft. 
apart.  The  rails  and  styles 
should  be  halved  together,  and 
they  and  the  diagonals  also 
should  have  a  J-in.  chamfer; 
the  sheathings  should  be  screwed  on.  Fig.  33  shows  a  door  of  the 
construction  described.  Tables  X.  and  XL  give  the  proper  sizes  of 
material  and  hardware  for  doors  of  different  sizes. 

TABLE  X.— Showing  Proper  Sizes  of  Material  for  Doors  up  to  14  x  20  ft.  in  Size. 


Size    of    Doors.  Styles. 

In  ft.  Ins. 

5  X  8  or  less 4x1% 

5  x  8  to  7  x  8 7x1% 

7  x  8  to  10  x  10 7xlV2 

10  x  10  to  14  x  14.  ..8x2 
14  x  14  to  14  x  20.  .9x2% 


1  — 
Top. 

Center. 

—  i 
Bottom. 

Diags. 

Sheath. 

Ins. 

Ins. 

Ins. 

Ins. 

Ins. 

4x1% 
7x1% 

4x1% 
6x1% 

6x1% 
8x1% 

4x1% 
4x1% 

4x% 

4x% 

7x1% 

6x1% 

8x1% 

4x1% 

4x% 

9x2 

8x2 

10x2 

5x2 

4x% 

9x2% 

8x2% 

10x2V2 

5x2% 

4x% 

MISCELLANEOUS   STRUCTURAL  DETAILS. 


33 


$"-> 


'•/I*  %° Brick  Rail  may  be 


Figs.  34  and  35. 


Corr,  Iron— 


Fkxshiry 


fZJ 


Fig,  36. 
Figs.  34  to  36.    Details  for  Side  Window  in  Brick  and  Iron  Frame    Walls. 


34 


MILL     BUILDING     CONSTRUCTION. 


TABLE  XI.  —  Showing  Dimensions  of  Hinges  and  Appurtenances   for  Doors   of 

Different   Sizes. 
Stanley  Works  Heavy  Hinges. 
I  -  Plain  -  1       |  —  'Galvanized.-^i      |  —  Screws.  —  j 

Size  of  doors.       Strap.         T.           Strap.             T.      Door.     Jamb.  Bolts. 

Ft.                  Ins.          Ins.             Ins.             Ins.      Ins.        Ins.  Ins. 

3x6  or  less..     10          10              10              10       1%          2  % 

3x6  to  3x8..    16           16              16              16       1%          2  V2 

3  X  8  to  4  X  10.  24-in.  strap  hinge  ............  %-in.  lag  screws.  y2 

4  x  10  to  5  x  12.  30-in.     "         "     ............     "           ««  y2 

Over  5  x  12..  .  36-in.     "         "     ............     "  y2 


-  34  shows  the  details  for  a  side  window  in  a  brick  wall.  Us- 
ing ioxi2-in.  glass,  these  windows  are  usually  made  with  from  24 
to  40  lights  or  panes.  The  sizes  of  wall  openings  required  for  win- 
dows with  from  24  to  40  ioxi2-in.  lights,  are  as  follows  : 

No.  of  lights.  Size  of  opening. 

24  ..................................  4  x  7  ft. 

28  ..................................  4x8  ft.  1  in. 

32  ..................................  4  x  9  ft.  1  in. 

40  ..................................  4  ft.  10  ins.  x  9  ft.  1  in. 

Figs.  35  and  36  shows  details  of  window  construction  in  the  side 
wall  of  an  iron  frame  building  covered  with  corrugated  iron. 

VENTILATORS.—  Ridge  ventilators  may 
be  in  the  form  of  a  monitor  roof  or  they  may 
be  round  ventilators  placed  at  intervals  (Fig. 
37).  The  area  of  ventilators  required  per  100 
sq.  ft.  of  floor  surface  for  shop  buildings  of  Fig  37 

various  kinds  is  given  in  square  feet  by  the 
following  table: 

Height,  in  ft.,  above  ground.  20  30     40  50 

Machine  shop,   sq.   ft  ......      %  %      %      %  Round  vents. 

Mills,   sq.   ft  ..............   7  6       5  4  Louvre  vents. 

Forge   shop,   sq.    ft  ........   9  8        7  6  Louvre  or  open  vents. 

The  areas  given  in  this  table  are  net  areas  and  when  louvres  are 
used  60$  should  be  added  to  allow  for  the  obstruction  of  the  open- 
ing by  the  slats.  The  areas  in  square  feet  of  round  ventilators  of 
different  diameter  are  as  follows  : 

Diameter,    ins..  .   12      18      24      36      38       42       48 

Area,    sq.    ft  ................     0.8     1.8     3.1     4.9     7.1     9.6     12.6 

Details  of  a  monitor  roof  ventilator  with  louvres  are  shown  by 
Fig.  38.  Fig.  39  shows  details  of  a  monitor  roof  ventilator  with 
hinged  flat  iron  shutters.  These  details  are  for  a  shutter  8  ft.  long. 
Ordinarily,  shutters  should  be  made  6,  7,  8,  9  or  10  ft.  long,  but  in- 
termediate lengths  may  be  used  if  necessary.  The  width  of  the  shut- 
ters should  be  the  same  for  all  lengths.  The  shutters  may  be  either 


MISCELLANEOUS   STRUCTURAL  DETAILS. 


35 


Louvres 
Fig.  38.     Monitor  Roof  Ventilator  with  Louvres. 


Roof,  Corrugated  Iron 


In  Laying  out-  Venti- 
'letters  Locate 
Purlins  in 


Locate     ^. 
;  in  Proper   X  t 
to  Fit  Bevel      \4 
tf  Ventilation     \ 


This  Hole  for  Third 
Hinge  for  Shutters 
fable       over  6'0' long 
Finish 


This  Demension  to  be?  in. 
less  than  Length  of  Shutter 


of  Standard  Ventilation 
Flashing.  / 

Skehh  for  Corr.  Iron  List 
Give  Dimension  "a  "only. 


<*& 


g'°Tie-Beam  Hook 
Fig.  39.    Monitor  Roof  Ventilators  with  Hinged  Flat  Iron  Shutters. 


MILL     BUILDING     CONSTRUCTION. 


* 


"->  <-B-—> 


T 


Fig.   40.    Mention   Roof  Ventilator  with    Fixed   Sash. 


Fig.  41.     Monitor  Roof  Ventilator  with  Movable  Sash. 


MILL     BUILDING     CONSTRUCTION. 


37 


Fig,  42. 


LI:::::: 

J—  . 

i    i 
i    j 

}  \ 

jl 

i    i 
i    i 

|         |    1  U  U  

_t  J      I  

i  1  1 
1  | 

J!  ii  - 

Fig,  43. 
Figs.  42  and  43.     Monitor  Roof  Ventilators  with  All-Wood  Framing. 


MILL     BUILDING     CONSTRUCTION. 


Dimensions  given  are  for 

LochJoirrr 


Detail  of 
Lap  Joint. 


Detail  of 
Lock  Joint. 


Detail  of 
Capped  Joint. 


Method   for  Fa£>tning 
Ends  of  Wire. 


Fig.  44.     Monitor  Roof  Skylight  of  Translucent  Fabric. 


Specimen     Drawing     of 
Gutter     Angles. 


Deta»\   of  Gutter 
with    L,    Purlins. 


Detail  of  Double  or  Va«ey  Outer- 

Fig.  45.    Single  and 'Double  Gutters. 


MILL     BUILDING     CONSTRUCTION. 


39 


Hanging  6utter 
Berger's    Patent  -Adjus-table  Hanger. 


For  Hanging  Gutters,  Punch  ff Holes 
in  Purlin  to  take  Hangers. 
Out  Edge  of  Gutter  must  not  Extend 
above  Roof  plane  prolonged. 


Hanging    6utter6  "D.B." 
Adjustable   Strap  Hanger. 


Details  of   Box  Oulter, 
Fig.  46.    Types  of  Fixed  and  Hanging  Gutters. 


4O  MILL     BUILDING     CONSTRUCTION. 

of  black  iron  or  galvanizd  iron.  If  galvanized  iron  is  used  all  cover- 
ing and  flashing  for  the  ventilator  roof,  sides  and  ends,  and  all  bolts, 
clips,  clinch  rivets  or  other  fastenings,  any  part  of  which  shows  on 
the  outside  of  the  covering  or  finishing,  should  also  be  galvanized. 
Fig.  40  shows  a  monitor  roof  ventilator  with  fixed  sash  and  all 
iron  framing,  and  Fig.  41  shows  a  similar  construction  with  mov- 
able sash.  Figs.  42  and  43  show  monitor  roof  ventilators  with 
fixed  and  swing  sash,  respectively,  all  wood  framing.  Fig.  44 
shows  a  skylight  on  roof  of  monitor  made  of  translucent  fab- 
ric. It  should  be  noted  that  the  roofing  sheets  run  lengthwise  of 
the  building  and  are  6  ft.  3  ins.  x  3  ft.  3  ins.  in  size.  This  size  of 
sheet  should  be  used  whenever  possible,  although  sheets  may  be 
readily  cut  to  smaller  sizes.  The  width  of  the  lap  should  be  2  ins. 
and  both  edges  should  be  securely  fastened.  For  fastening  the  fab- 
ric wire  nails  ij-in.  long,  or  3d  nails,  should  be  used;  the  amount 
required  being  ij  Ibs.  per  100  ft.  of  seam.  Lap  joints  or  lock  joints 
can  be  used  for  all  seams,  but  capped  joints  can  be  used  only  for 
seams  running  in  the  direction  of  the  roof  slope. 

GUTTERS  AND  DOWN  SPOUTS.— The  sizes  of  gutters  and 
down  spouts  and  their  distance  apart  for  roofs  with  J  pitch  and  of 
different  spans  are  shown  by  the  following  table : 

1/2   roof   span,    ft.                                     10  20    30    40    50    60    70    80 

Size  of  gutter,  ins 5  5      6      6      7      7      8      8 

Size  of  down  spouts,  ins 3  3445566 

Spacing  of  down  spouts,  ft 50  50    50    50    40    40    40    40 

The  slope  of  gutters  should  be  at  least  i  ft.  in  50  ft.  When  the 
length  of  the  roof  overruns  the  spacing  more  than  10  ft.  an  extra 
down  spout  should  be  put  on. 

Fig.  45  shows  details  of  single  and  double  gutters  with  both  an- 
gle and  channel  purlin  connections,  and  Fig.  46  shows  different 
forms  of  hanging  and  box  gutters.  Regarding  hanging  gutters  it 
may  be  noted  that  ordinarily  gutters  should  slope  I  in.  in  15  ft.  A 
6-in.  gutter  takes  a  4-in.  leader  and  will  drain  about  3,000  sq.  ft.  of 
horizontal  surface.  A  4-in.  gutter  will  take  a  3-in.  leader  and  will 
drain  about  1,700  sq.  ft.  of  horizontal  surface.  Hangers  for  hang- 
ing gutters  should  be  spaced  about  2  ft.  6  ins.  apart. 


UNIVERSITY  OF  CALIFORNIA  LIBRARY, 
BERKELEY 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 

Books  not  returned  on  time  are  subject  to  a  fine  of 
50c  per  volume  after  the  third  day  overdue,  increasing 
to  $1.00  per  volume  after  the  sixth  day.  Books  not  in 
demand  may  be  renewed  if  application  is  made  before 
expiration  of  loan  period. 


OCT  11  1944 


MAY    519677 


.MIL  23  2002 

U.C.BERKELEY 


4  '67  -3PM 


LO/ 


lOm-4,'23 


VC   1280 


ttilMilliiiiiJi  iiiliii 


